Conventionally, a hydraulic control device for a loader is known in which a lift arm having a working implement, such as a bucket, at its end is brought into a floating state in a front loader, i.e., in which a lift arm is brought into a state of being freely moved up and down while keeping the working implement provided at the end of the arm in contact with the ground by simultaneously draining oil from an expansion oil chamber and from a contraction oil chamber of a lift cylinder by which the lift arm is moved up and down (see Japanese Published Unexamined Patent Application No. 2001-124011, which is hereinafter referred to as “patent document 1”).
However, in the hydraulic control device for a loader disclosed by patent document 1, a first valve mechanism that is a multi-direction changeover valve including direction changeover valves that control a pressure-oil supply to each actuator is disposed on the side of a driver's seat in a tractor, whereas a second valve mechanism that is a float mechanism used to create a floating state is disposed on the side of the front loader. Since the float mechanism and the multi-direction changeover valve are provided separately from each other in this way, pipes through which these valve mechanisms are connected together are needed. Additionally, since the device size is increased even if the float mechanism and the multi-direction changeover valve described in patent document 1 are formed integrally with each other, there is a risk that a great increase in cost may be caused.
Additionally, conventionally, a hydraulic control device for a loader is known in which, in a front loader including an arm and a bucket provided as an attachment to the end of the arm, the bucket is moved in a state of being parallel to the ground surface (i.e., horizontal to the ground surface) while a constant angle with the ground surface is maintained when the arm is manipulated (see Japanese Published Unexamined Patent Application No. H7-252857, which is hereinafter referred to as “patent document 2”). The hydraulic control device for a loader disclosed by patent document 2 includes an arm direction changeover valve that controls a supply of pressure oil to an arm cylinder, a bucket direction changeover valve that controls a supply of pressure oil to a bucket cylinder, and a flow dividing mechanism through which, when the arm is manipulated, the bucket is moved in a parallel state by dividing the flow of the pressure oil returned from the arm cylinder and then supplying a part of the pressure oil to the bucket cylinder when the arm direction changeover valve is operated. In the hydraulic control device for a loader disclosed by document 2, the arm direction changeover valve, the bucket direction changeover valve, and the flow dividing mechanism are united together.
However, in the hydraulic control device for a loader of patent document 2 (Japanese Published Unexamined Patent Application No. H7-252857), the flow dividing mechanism is disposed between the arm direction changeover valve and the bucket direction change over valve. The flow dividing mechanism includes a flow dividing valve (i.e., a flow dividing valve 20a) and a return oil passage open-close valve (i.e., a brake valve 19). The flow dividing valve divides the flow of the pressure oil returned from the arm cylinder and then supplies part of the pressure oil to the bucket cylinder when the arm direction changeover valve is operated. The return oil passage open-close valve opens or closes a return oil passage through which pressure oil returned from the bucket cylinder flows when the bucket is moved in a parallel state. The flow dividing valve and the return oil passage open-close valve are disposed side by side in this order between the arm direction changeover valve and the bucket direction changeover valve. Therefore, even if the arm direction changeover valve, the bucket direction changeover valve, and the flow dividing mechanism are formed to be united together, the hydraulic control device for a loader is elongated in one direction, and is increased in size. As a result, disadvantageously, in a material handling machine, it becomes difficult to secure a space for disposing the hydraulic control device for a loader. Additionally, in the hydraulic control device for a loader of patent document 2, relief valves (i.e., a relief valve 16 and a relief valve 18) are disposed along a direction in which the arm direction changeover valve, the flow dividing mechanism, and the bucket direction changeover valve are disposed side by side. Therefore, the hydraulic control device for a loader is further elongated in one direction, and is increased in size, thus it becomes difficult to secure a space for disposing the device. Additionally, when a variable throttle that adjusts the amount of oil, which is part of the pressure oil returned from the arm cylinder and which is selectively flowed to the bucket cylinder, is attached to the flow dividing valve, the hydraulic control device for a loader will be increased in size and will have difficulty in obtaining a space to be disposed if the variable throttle is united with the arm direction changeover valve and the bucket direction changeover valve without changing the form of the variable throttle.